- Documentation Library
- Table of Contents
- MySQL 3.23/4.0/4.1 Manual
- Table of Contents
Section Navigation [Toggle]
- 10.6 空間分析の最適化
- 10.6.1 空間インデックスの作成
- 10.6.2 空間インデックスの使用
MBRContains() や
MBRWithin() などの関数を
WHERE
句で使用するクエリの検索で空間インデックスを使用できるかどうかが、オプティマイザによって確認されます。
たとえば、指定された矩形に含まれているオブジェクトをすべて検索する必要があるとします。
mysql>SELECT fid,AsText(g) FROM geom WHEREmysql>MBRContains(GeomFromText('Polygon((30000 15000,31000 15000,31000 16000,30000 16000,30000 15000))'),g);+-----+-----------------------------------------------------------------------------+ | fid | AsText(g) | +-----+-----------------------------------------------------------------------------+ | 21 | LINESTRING(30350.4 15828.8,30350.6 15845,30333.8 15845,30333.8 15828.8) | | 22 | LINESTRING(30350.6 15871.4,30350.6 15887.8,30334 15887.8,30334 15871.4) | | 23 | LINESTRING(30350.6 15914.2,30350.6 15930.4,30334 15930.4,30334 15914.2) | | 24 | LINESTRING(30290.2 15823,30290.2 15839.4,30273.4 15839.4,30273.4 15823) | | 25 | LINESTRING(30291.4 15866.2,30291.6 15882.4,30274.8 15882.4,30274.8 15866.2) | | 26 | LINESTRING(30291.6 15918.2,30291.6 15934.4,30275 15934.4,30275 15918.2) | | 249 | LINESTRING(30337.8 15938.6,30337.8 15946.8,30320.4 15946.8,30320.4 15938.4) | | 1 | LINESTRING(30250.4 15129.2,30248.8 15138.4,30238.2 15136.4,30240 15127.2) | | 2 | LINESTRING(30220.2 15122.8,30217.2 15137.8,30207.6 15136,30210.4 15121) | | 3 | LINESTRING(30179 15114.4,30176.6 15129.4,30167 15128,30169 15113) | | 4 | LINESTRING(30155.2 15121.4,30140.4 15118.6,30142 15109,30157 15111.6) | | 5 | LINESTRING(30192.4 15085,30177.6 15082.2,30179.2 15072.4,30194.2 15075.2) | | 6 | LINESTRING(30244 15087,30229 15086.2,30229.4 15076.4,30244.6 15077) | | 7 | LINESTRING(30200.6 15059.4,30185.6 15058.6,30186 15048.8,30201.2 15049.4) | | 10 | LINESTRING(30179.6 15017.8,30181 15002.8,30190.8 15003.6,30189.6 15019) | | 11 | LINESTRING(30154.2 15000.4,30168.6 15004.8,30166 15014.2,30151.2 15009.8) | | 13 | LINESTRING(30105 15065.8,30108.4 15050.8,30118 15053,30114.6 15067.8) | | 154 | LINESTRING(30276.2 15143.8,30261.4 15141,30263 15131.4,30278 15134) | | 155 | LINESTRING(30269.8 15084,30269.4 15093.4,30258.6 15093,30259 15083.4) | | 157 | LINESTRING(30128.2 15011,30113.2 15010.2,30113.6 15000.4,30128.8 15001) | +-----+-----------------------------------------------------------------------------+ 20 rows in set (0.00 sec)
このクエリがどのように実行されるかを、EXPLAIN
を使用して確認します。
mysql>EXPLAIN SELECT fid,AsText(g) FROM geom WHEREmysql>MBRContains(GeomFromText('Polygon((30000 15000,31000 15000,31000 16000,30000 16000,30000 15000))'),g);+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+-------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | geom | range | g | g | 32 | NULL | 50 | Using where | +----+-------------+-------+-------+---------------+------+---------+------+------+-------------+ 1 row in set (0.00 sec)
空間インデックスがないとどうなるかを確認します。
mysql>EXPLAIN SELECT fid,AsText(g) FROM g IGNORE INDEX (g) WHEREmysql>MBRContains(GeomFromText('Polygon((30000 15000,31000 15000,31000 16000,30000 16000,30000 15000))'),g);+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+-------+-------------+ | 1 | SIMPLE | geom | ALL | NULL | NULL | NULL | NULL | 32376 | Using where | +----+-------------+-------+------+---------------+------+---------+------+-------+-------------+ 1 row in set (0.00 sec)
上記のクエリを実行し、使用可能な空間キーを無視します。
mysql>SELECT fid,AsText(g) FROM geom IGNORE INDEX (g) WHEREmysql>MBRContains(GeomFromText('Polygon((30000 15000,31000 15000,31000 16000,30000 16000,30000 15000))'),g);+-----+-----------------------------------------------------------------------------+ | fid | AsText(g) | +-----+-----------------------------------------------------------------------------+ | 1 | LINESTRING(30250.4 15129.2,30248.8 15138.4,30238.2 15136.4,30240 15127.2) | | 2 | LINESTRING(30220.2 15122.8,30217.2 15137.8,30207.6 15136,30210.4 15121) | | 3 | LINESTRING(30179 15114.4,30176.6 15129.4,30167 15128,30169 15113) | | 4 | LINESTRING(30155.2 15121.4,30140.4 15118.6,30142 15109,30157 15111.6) | | 5 | LINESTRING(30192.4 15085,30177.6 15082.2,30179.2 15072.4,30194.2 15075.2) | | 6 | LINESTRING(30244 15087,30229 15086.2,30229.4 15076.4,30244.6 15077) | | 7 | LINESTRING(30200.6 15059.4,30185.6 15058.6,30186 15048.8,30201.2 15049.4) | | 10 | LINESTRING(30179.6 15017.8,30181 15002.8,30190.8 15003.6,30189.6 15019) | | 11 | LINESTRING(30154.2 15000.4,30168.6 15004.8,30166 15014.2,30151.2 15009.8) | | 13 | LINESTRING(30105 15065.8,30108.4 15050.8,30118 15053,30114.6 15067.8) | | 21 | LINESTRING(30350.4 15828.8,30350.6 15845,30333.8 15845,30333.8 15828.8) | | 22 | LINESTRING(30350.6 15871.4,30350.6 15887.8,30334 15887.8,30334 15871.4) | | 23 | LINESTRING(30350.6 15914.2,30350.6 15930.4,30334 15930.4,30334 15914.2) | | 24 | LINESTRING(30290.2 15823,30290.2 15839.4,30273.4 15839.4,30273.4 15823) | | 25 | LINESTRING(30291.4 15866.2,30291.6 15882.4,30274.8 15882.4,30274.8 15866.2) | | 26 | LINESTRING(30291.6 15918.2,30291.6 15934.4,30275 15934.4,30275 15918.2) | | 154 | LINESTRING(30276.2 15143.8,30261.4 15141,30263 15131.4,30278 15134) | | 155 | LINESTRING(30269.8 15084,30269.4 15093.4,30258.6 15093,30259 15083.4) | | 157 | LINESTRING(30128.2 15011,30113.2 15010.2,30113.6 15000.4,30128.8 15001) | | 249 | LINESTRING(30337.8 15938.6,30337.8 15946.8,30320.4 15946.8,30320.4 15938.4) | +-----+-----------------------------------------------------------------------------+ 20 rows in set (0.46 sec)
空間インデックスを使用しないと、このクエリの実行時間は 0.00 秒から 0.46 秒に増大します。
将来のリリースでは、空間インデックスを使用して他の関数も最適化されるようになります。 See 項10.5.4. 「ジオメトリオブジェクト間の空間的関係をテストするための関数」。
This is a translation of the MySQL Reference Manual that can be found at dev.mysql.com. The original Reference Manual is in English, and this translation is not necessarily as up to date as the English version.
